Light emitting device having a lateral passivation layer

ABSTRACT

Provided are a light emitting device, a light emitting device package, and a lighting system. The light emitting device includes a light emitting structure including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer between the first conductive type semiconductor layer and the second conductive type semiconductor layer, and a passivation layer protecting a surface of the light emitting structure. The passivation layer includes a first passivation layer on a top surface of the light emitting structure and a second passivation layer having a refractive index different from that of the first passivation layer, the second passivation layer being disposed on a side surface of the light emitting structure. The second passivation layer has a refractive index greater than that of the first passivation layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/016,217 filed on Jan. 28, 2011 now U.S. Pat. No. 8,071,973 claimingthe benefit of Korean Patent Application No. 10-2010-0009211 filed Feb.1, 2010, both of which are hereby incorporated by reference for allpurpose as if fully set forth herein.

BACKGROUND

Embodiments relate to a light emitting device, a light emitting devicepackage, and a lighting system.

In light emitting devices, P-N junction diodes having the properties ofconverting electrical energy into light energy may be formed bycombining group III and V elements on the periodic table. Light emittingdevices may realize various colors by controlling the composition ratioof compound semiconductors.

Nitride semiconductors are attracting much attention for the fields ofoptical devices and high-power electronic devices because of their highthermal stability and wide band gap energy. In particular, blue lightemitting devices, green light emitting devices, and UV light emittingdevices, which use nitride semiconductors have been commercialized andare widely used.

According to a related art, a passivation layer is disposed on a sidesurface of a light emitting device. When a single-layered passivationlayer having the same refractive index is disposed on a side surface anda top surface of the light emitting device, it is difficult to obtain anoptimized light amount. This is done because a reflective index layersatisfying an anti-reflection coating condition is disposed on a sidesurface and an optimized reflective index layer on the top surface ischanged according to a period of a light extraction pattern.

Since diffraction efficiency of the light extraction pattern depends ona refractive index of an interface, a refractive index of thepassivation layer filling the pattern may become an important parameter.

SUMMARY

Embodiments provide a light emitting device, which can obtain anoptimized light amount, a light emitting device package, and a lightingsystem.

In one embodiment, a light emitting device includes: a light emittingstructure including a first conductive type semiconductor layer, asecond conductive type semiconductor layer, and an active layer betweenthe first conductive type semiconductor layer and the second conductivetype semiconductor layer; and a passivation layer protecting a surfaceof the light emitting structure, wherein the passivation layer includes:a first passivation layer on a top surface of the light emittingstructure; and a second passivation layer having a refractive indexdifferent from that of the first passivation layer, the secondpassivation layer being disposed on a side surface of the light emittingstructure, wherein the second passivation layer has a refractive indexgreater than that of the first passivation layer.

In another embodiment, a light emitting device includes: a lightemitting structure including a first conductive type semiconductorlayer, a second conductive type semiconductor layer, and an active layerbetween the first conductive type semiconductor layer and the secondconductive type semiconductor layer; and a passivation layer protectinga surface of the light emitting structure, wherein the passivation layerincludes: a first passivation layer on a top surface of the lightemitting structure; and a second passivation layer having a refractiveindex different from that of the first passivation layer, the secondpassivation layer being disposed on a side surface of the light emittingstructure, wherein the second passivation layer may satisfy ananti-reflection coating condition.

In further another embodiment, a light emitting device includes: a lightemitting structure including a first conductive type semiconductorlayer, a second conductive type semiconductor layer, and an active layerbetween the first conductive type semiconductor layer and the secondconductive type semiconductor layer; and a passivation layer protectinga surface of the light emitting structure, wherein the passivation layerincludes: a first passivation layer on a top surface of the lightemitting structure; and a second passivation layer having a refractiveindex different from that of the first passivation layer, the secondpassivation layer being disposed on a side surface of the light emittingstructure, wherein the second passivation layer may have a thickness of(λ/4n)×(2m+1) (where, λ is a wavelength of light emitted from the activelayer, n is a refractive index of the light emitting structure, and m iszero or a positive integer).

In still further another embodiment, a light emitting device includes: alight emitting structure including a first conductive type semiconductorlayer, a second conductive type semiconductor layer, and an active layerbetween the first conductive type semiconductor layer and the secondconductive type semiconductor layer; and a passivation layer protectinga surface of the light emitting structure, wherein the passivation layerincludes: a first passivation layer on a top surface of the lightemitting structure; and a second passivation layer having a refractiveindex different from that of the first passivation layer, the secondpassivation layer being disposed on a side surface of the light emittingstructure, wherein a light extraction structure is disposed on the lightemitting structure.

In even further another embodiment, a light emitting device includes: alight emitting structure including a first conductive type semiconductorlayer, a second conductive type semiconductor layer, and an active layerbetween the first conductive type semiconductor layer and the secondconductive type semiconductor layer; and a passivation layer protectinga surface of the light emitting structure, wherein the passivation layerincludes: a first passivation layer on a top surface of the lightemitting structure; and a second passivation layer having a refractiveindex different from that of the first passivation layer, the secondpassivation layer being disposed on a side surface of the light emittingstructure, wherein at least one layer of the first passivation layer andthe second passivation layer may include the light extraction structureon a surface thereof.

In yet further another embodiment, a light emitting device includes: alight emitting structure including a first conductive type semiconductorlayer, a second conductive type semiconductor layer, and an active layerbetween the first conductive type semiconductor layer and the secondconductive type semiconductor layer; and a passivation layer protectinga surface of the light emitting structure, wherein the passivation layerincludes: a first passivation layer on a top surface of the lightemitting structure; and a second passivation layer having a refractiveindex different from that of the first passivation layer, the secondpassivation layer being disposed on a side surface of the light emittingstructure, wherein the light emitting structure has an inclined sidesurface.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a light emitting device according to afirst embodiment.

FIGS. 2 to 5 are sectional views illustrating a process of manufacturingthe light emitting device according to the first embodiment.

FIG. 6 is a sectional view of a light emitting device according to asecond embodiment.

FIG. 7 is a sectional view of a light emitting device according to athird embodiment.

FIG. 8 is a sectional view of a light emitting device according to afourth embodiment.

FIG. 9 is a sectional view of a light emitting device according to afifth embodiment.

FIG. 10 is a sectional view of a light emitting device package accordingto an embodiment.

FIG. 11 is a perspective view of a lighting unit according to anembodiment.

FIG. 12 is an exploded perspective view of a backlight unit according toan embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a light emitting device, a light emitting device package,and a lighting system according to an embodiment will be described withreference to accompanying drawings.

In the description of embodiments, it will be understood that when alayer (or film) is referred to as being ‘on’ another layer or substrate,it can be directly on another layer or substrate, or intervening layersmay also be present. Further, it will be understood that when a layer isreferred to as being ‘under’ another layer, it can be directly underanother layer, and one or more intervening layers may also be present.In addition, it will also be understood that when a layer is referred toas being ‘between’ two layers, it can be the only layer between the twolayers, or one or more intervening layers may also be present.

Embodiments

FIG. 1 is a sectional view of a light emitting device according to afirst embodiment.

A light emitting device 101 according to embodiments may include a lightemitting structure 110, a first passivation layer 131 on a top surfaceof the light emitting structure 110, and a second passivation layer 132on a side surface of the light emitting structure 110.

The second passivation layer 132 may be disposed on the firstpassivation layer 131 on the top surface of the light emitting structure110.

The second passivation layer 132 may have a refractive index greaterthan that of the first passivation layer 131, but is not limitedthereto.

The second passivation layer 132 may have a thickness less than that ofthe first passivation layer 131, but is not limited thereto.

The first passivation layer 131 may have a refractive index less thanthat of the light emitting structure 110.

The second passivation layer 132 may be formed to satisfy ananti-reflection coating condition.

For example, the second passivation layer 132 may have a thickness of(λ/4n)+(2m+1) (where, λ is a wavelength of light emitted from an activelayer 114, n is a refractive index of the light emitting structure 110,and m is zero or a positive integer).

The current embodiment may include a light extraction structure P on thelight emitting structure 110.

The first passivation layer 131 may be disposed along a surface shape ofthe light extraction structure P.

Also, according to the current embodiment, a side surface of the lightemitting structure 110 may be inclined as shown in FIGS. 7 and 8.

In this case, the second passivation layer 132 may have a thickness of(λ/4n)×(2m+1)/cos(x) (where, m is zero or a positive integer, x is anangle between zero and θ, and θ is an inclined angle of the side surfaceof the light emitting structure).

The current embodiment may introduce a passivation layer 130 to preventa leakage current of an LED chip from occurring.

Since band gaps of electrons are disposed with spatial periodicity in aquantum well layer of a light emitting device, the periodicity may bebroken when the quantum well layer is exposed to the outside in anisolation process. Thus, a new energy level may be generated around theband gap.

The generated energy level is referred to as a surface state. Since thesurface state generally undergoes a non-radiative recombination process,electrons supplied to the surface state does not generate light, but isconverted into heat. Thus, when a current is injected into the lightemitting device, the quantum well layer around a side surface of anisolation layer may be degraded. The degradation of the quantum welllayer may affect reliability of the device. To solve such a limitation,the side surface of the quantum well layer exposed to the outside may beprotected by a dielectric material. Such a dielectric layer may bereferred to as a passivation layer.

The passivation layer may be formed of an oxide-, nitride-, orfluoride-based compound, but is not limited thereto.

In case of a vertical type GaN LED, a passivation layer may cover sidesurfaces and a top surface of a chip. Since the passivation layer isdisposed within a light emitting path, a refractive index and a lightabsorption of the passivation layer may be important parameters withrespect to an amount of light. Specifically, since the passivation layerdisposed on the top surface of the light emitting structure contacts alight extraction pattern, functions of the passivation may be veryimportant.

According to the current embodiment, in a multi-passivation layer 130,the first passivation layer 131 contacting the light extractionstructure P disposed on a top surface of the light emitting device chipmay be disposed, and then, the second passivation layer 132 contacting aside surface of the light extraction structure P may be disposed.

Here, the first passivation and the second passivation 132 may haverefractive indexes different from each other. For example, the firstpassivation layer 131 may have a refractive index between about 1.4 toabout 2.0 according a period of the light extraction structure P, but isnot limited thereto.

Also, the second passivation layer 132 may have a refractive index ofabout 1.57 (in a case where a background material is air) or about 1.89(in a case where a background material is Si gel, where it is assumedthat n=1.45) to satisfy an anti-reflection condition (a geometric meanof refractive indexes of both materials constituting an interface)according to the refractive indexes of the background materials, but isnot limited thereto. Here, it may be assumed that the light emittingstructure is formed of GaN and the GaN has a refractive index of about2.46, but is not limited thereto.

According to the current embodiment, the second passivation layer 132disposed on the side surfaces of the light emitting structure maysatisfy the anti-reflection coating condition. However, the firstpassivation layer 131 disposed on the top surface of the light emittingstructure may be formed of a material having a refractive index lessthan that of the second passivation in consideration of the refractiveindex of the light emitting structure and the period of the lightextraction structure to obtain optimized light extraction efficiency.

In the light emitting device according to the current embodiment, themulti-passivation layer having the refractive indexes different fromeach other may be disposed on the side surface and the top surface ofthe light emitting structure to obtain an optimized light amount.

Hereinafter, a process of manufacturing a light emitting deviceaccording to a first embodiment will be described with reference toFIGS. 2 to 5.

First, a light emitting structure 110 is formed. For example, the lightemitting structure 110 may include a first conductive type semiconductorlayer 112, an active layer 114, and a second conductive typesemiconductor layer 116.

First, a first substrate (not shown) is prepared as shown in FIG. 2. Thefirst substrate may include a conductive substrate or an insulativesubstrate. For example, the first substrate may be formed of at leastone of sapphire (Al₂O₃), SiC, GaAs, GaN, ZnO, Si, GaP, InP, Ge, andGa₂O₃. A roughness structure may be formed on the first substrate, butis not limited thereto.

A wet etching process may be performed on the first substrate to removeimpurities on the first substrate.

Thereafter, the light emitting structure 110 including the firstconductive type semiconductor layer 112, the active layer 114, and thesecond conductive type semiconductor layer 116 may be formed on thefirst substrate.

For example, the light emitting structure 110 may be formed using one ofa metal organic chemical vapor deposition (MOCVD) process, a chemicalvapor deposition (CVD) process, a plasma-enhanced chemical vapordeposition (PECVD) process, a molecular beam epitaxy (MBE) process, anda hydride vapor phase epitaxy (HVPE) process, but is not limitedthereto.

A buffer layer (not shown) may be formed on the first substrate. Thebuffer layer may reduce a lattice mismatch between a material of thelight emitting structure 110 and the first substrate. The buffer layermay be formed of a group III-V compound semiconductor, e.g., at leastone of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN. An undopedsemiconductor layer may be formed on the buffer layer, but is notlimited thereto.

The first conductive type semiconductor layer 112 may be formed of agroup III-V compound semiconductor doped with a first conductive typedopant. When the first conductive type semiconductor layer 112 is anN-type semiconductor layer, the first conductive type dopant may includeSi, Ge, Sn, Se, or Te as an N-type dopant, but is not limited thereto.

The first conductive type semiconductor layer 112 may be formed of asemiconductor material having a compositional formula ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1).

The first conductive type semiconductor layer 112 may be formed of oneof GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs,AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, and InP.

The first conductive type semiconductor layer 112 may form an N-type GaNlayer using the CVD process, the MBE process, a sputtering process, orthe HVPE process. Also, the first conductive type semiconductor layer112 may be formed by injecting silane gas (SiH₄) containing n-typeimpurities such as trimethyl gallium (TMGa) gas, ammonia (NH₃) gas,nitrogen (N₂) gas, and silicon (Si).

The active layer 114 is a layer in which electrons injected through thefirst conductive type semiconductor layer 112 meet with holes injectedthrough the second conductive type semiconductor layer 116 to emit lighthaving energy determined by a proper energy band of the active layer(light emitting layer) material.

The active layer 114 may have at least one of a single quantum wellstructure, a multi quantum well (MQW) structure, a quantum-wirestructure, and a quantum dot structure. For example, the active layer114 may have the MQW structure by injecting trimethyl gallium (TMGa)gas, ammonia (NH₃) gas, nitrogen (N₂) gas, and trimethyl indium (TMIn)gas, but is not limited thereto.

A well layer/barrier layer of the active layer 114 may have a pairstructure with at least one of InGaN/GaN, InGaN/InGaN, AlGaN/GaN,InAlGaN/GaN, GaAs(InGaAs)/AlGaAs, and GaP(InGaP)/AlGaP, but is notlimited thereto. The well layer may be formed of a material having aband gap less than that of the barrier layer.

A conductive type clad layer may be formed on or/and under the activelayer 114. The conductive type clad layer may be formed of anAlGaN-based semiconductor and have a band gap greater than that of theactive layer 114.

The second conductive type semiconductor layer 116 may be formed of agroup III-V compound semiconductor doped with a second conductive typedopant, e.g., a semiconductor material having a compositional formula ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). For example, the secondconductive type semiconductor layer 116 may be formed of one of GaN,AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, AlGaAs, GaP, GaAs, GaAsP, andAlGaInP. When the second conductive type semiconductor layer 116 is aP-type semiconductor layer, the second conductive type dopant mayinclude Mg, Zn, Ca, Sr, or Ba as a P-type dopant. The second conductivetype semiconductor layer 116 may have a single-layered or multi-layeredstructure, but is not limited thereto.

The second conductive type semiconductor layer 116 may form a P-type GaNlayer by injecting trimethyl gallium (TMGa) gas, ammonia (NH₃) gas,nitrogen (N₂) gas, and trimethyl indium (TMIn) gas, andbis-ethyl-cyclopentadienyl-magnesium (EtCp₂Mg) {Mg(C₂H₅C₅H₄)₂}containing P-type impurities such as magnesium (Mg) into a chamber, butis not limited thereto.

In the current embodiment, the first conductive type semiconductor layer112 may be realized as an N-type semiconductor layer, and the secondconductive type semiconductor layer 126 may be realizes as a P-typesemiconductor layer, but are not limited thereto. Also, a semiconductorlayer having a polarity opposite to that of the second conductive type,e.g., an N-type semiconductor layer (not shown) may be formed on thesecond conductive type semiconductor layer 116. Thus, the light emittingstructure 110 may have one of an N-P junction structure, a P-N junctionstructure, an N-P-N junction structure, and a P-N-P junction structure.

Thereafter, a second electrode layer 120 is formed on the secondconductive type semiconductor layer 116.

The second electrode layer 120 may include an ohmic layer (not shown), areflective layer (not shown), an adhesion layer (not shown), and aconductive support layer (not shown).

For example, the second electrode layer 120 may include the ohmic layer(not shown). The ohmic layer ohmic-contacts the light emitting structure110 to smoothly supply a power to the light emitting structure 110.Also, the ohmic layer may be formed by multiply stacking a single metalor a metal alloy and a metal oxide.

For example, the ohmic layer may be formed of at least one of indium tinoxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO),indium aluminum zinc oxide (IAZO), indium gallium zinc oxide (IGZO),indium gallium tin oxide (IGTO), aluminum zinc oxide (AZO), antimony tinoxide (ATO), gallium zinc oxide (GZO), IZO Nitride (IZON), Al—Ga ZnO(AGZO), In—Ga ZnO (IGZO), ZnO, IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au,Ni/IrOx/Au/ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, andHf, but is not limited thereto.

The second electrode layer 120 includes the reflective layer (not shown)to reflect light incident from the light emitting structure 110, therebyimproving the light extraction efficiency.

For example, the reflective layer may be formed of a metal or alloyincluding at least one of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au,Hf. Also, the reflective layer may be formed in a multi-layeredstructure using the metal or alloy and a light-transmitting conductivematerial such as IZO, IZTO, IAZO, IGZO, IGTO, AZO, or ATO. For example,the reflective layer may have a stacked structure of IZO/Ni, AZO/Ag,IZO/Ag/Ni, or AZO/Ag/Ni.

When the second electrode layer 120 includes the adhesion layer, thereflective layer may serve as an adhesion layer or include a barriermetal or a bonding metal. For example, the adhesion layer may be formedof at least one of Tl, Au, Sn, Ni, Cr, Ga, In, Bi, Cu, Ag and Ta.

The second electrode layer 120 may include the conductive supportsubstrate. The conductive support substrate supports the light emittingstructure 110 and provides a power to the light emitting structure 110.The conductive support substrate may be formed of a metal, a metalalloy, or a conductive semiconductor material, which has superiorconductivity.

For example, the conductive support substrate may be formed of at leastone of copper (Cu), a copper alloy, gold (Au), nickel (Ni), molybdenum(Mo), copper-tungsten (Cu—W), and a carrier wafer (e.g., Si, Ge, GaAs,GaN, ZnO, SiGe, or SiC).

The conductive support substrate may have a thickness, which is variedaccording to the design of the light emitting device 110. For example,the conductive support substrate may have a thickness of about 30 μm to500 μm.

A process of forming the conductive support substrate may include anelectrochemical metal deposition process, a plating process, and abonding process using a eutectic metal.

Thereafter, the first substrate is removed to expose the firstconductive type semiconductor layer 112. The first substrate may beremoved using a laser lift off process or a chemical lift off process.Alternatively, the first substrate may be removed through physicalgrinding.

Next, the current embodiment may include a process of forming a lightextraction structure P on the light emitting structure 110 after theforming of the light emitting structure 110.

For example, the light extraction structure P may have an unevenness oroptical crystal structure, but is not limited thereto. The lightextraction structure P may be formed through a wet etching or dryetching process.

Next, a passivation layer 130 is formed on the light emitting structure110.

In the current embodiment, a first passivation layer 131 may be firstlydisposed on a top surface contacting the light extraction structure P,and a second passivation layer 132 surrounding side surfaces of thefirst passivation layer 131 and the light emitting structure 110 may beadditionally disposed.

For example, as shown in FIG. 3, the first passivation layer 131 isformed on the top surface of the light emitting structure 110. Here,since the first passivation layer 131 is formed along a surface shape ofthe light extraction structure P to allow a surface of the firstpassivation layer 131 to maintain the surface shape of the lightextraction structure P, the light extraction efficiency may be improved.

In the current embodiment, the first passivation layer 131 may have arefractive index less than that of the light emitting structure 110.

In the current embodiment, the first passivation layer 131 may have anoptimized refractive index, which is differently set according to aperiod of the light extraction structure P contacting the firstpassivation layer 131.

For example, the first passivation layer 131 may have a refractive indexbetween about 1.4 to about 2.0 according to the period of the lightextraction structure P, but is not limited thereto.

Next, as shown in FIG. 4, the second passivation layer 132 may be formedon a side surface of the light emitting structure 110.

The second passivation layer 132 may be formed also on the firstpassivation layer 131 formed on the top surface of the light emittingstructure 110.

The second passivation layer 132 may be formed along the surface shapeof the first passivation layer 131 to improve the light extractionefficiency.

Also, when a predetermined mask pattern (not shown) may be formed, thesecond passivation layer 132 may not be formed in a pad electrode regionthat will be formed later, but is not limited thereto.

In the current embodiment, the second passivation layer 132 may have arefractive index greater than that of the first passivation layer 131,but is not limited thereto.

Also, the second passivation layer 132 may be formed to satisfy ananti-reflection coating condition, but is not limited thereto. Also, thesecond passivation layer 132 may have a refractive index less than thatof the light emitting structure 110.

For example, the second passivation layer 132 may have a refractiveindex of about 1.57 (in a case where a background material is air) orabout 1.89 (in a case where a background material is Si gel, where it isassumed that n=1.45) to satisfy an anti-reflection condition (ageometric mean of refractive indexes of both materials constituting aninterface) according to the refractive indexes of the backgroundmaterials, but is not limited thereto. Here, it may be assumed that thelight emitting structure is formed of GaN and the GaN has a refractiveindex of about 2.46, but is not limited thereto.

In the first embodiment, the second passivation layer 132 may have athickness of (λ/4n)×(2m+1) (where, λ is a wavelength of light emittedfrom an active layer, n is a refractive index of the light emittingstructure, and m is zero or a positive integer).

According to the current embodiment, the second passivation layer 132disposed on the side surfaces of the light emitting structure maysatisfy the anti-reflection coating condition. However, the firstpassivation layer 131 disposed on the top surface of the light emittingstructure may be formed of a material having a refractive index lessthan that of the second passivation in consideration of the refractiveindex of the light emitting structure and the period of the lightextraction structure to obtain optimized light extraction efficiency.

Next, as shown in FIG. 5, a portion of the first passivation layer 131in the pad electrode region may be removed to expose the top surface ofthe light emitting structure, thereby forming a pad electrode 140.

In the light emitting device according to the current embodiment, themulti-passivation layer having the refractive indexes different fromeach other may be disposed on the side surface and the top surface ofthe light emitting structure to obtain an optimized light amount.

FIG. 6 is a sectional view of a light emitting device 102 according to asecond embodiment.

A second embodiment may adopt the technical features of the firstembodiment.

In the second embodiment, a third passivation layer 133 may be mainlydisposed on a side surface of a light emitting structure 110. Also, thethird passivation layer 133 may not be hardly disposed on a top surfaceof the light emitting structure. As shown in FIG. 6, the thirdpassivation layer 133 may partially overlap a first passivation layer131, but is not limited thereto.

According to the second embodiment, the first passivation layer 131 maybe formed of a material adequate for improving light extractionefficiency. Also, the third passivation layer 133 may be formed of amaterial, which satisfies an anti-reflection coating condition. Thus,the passivation layers may be formed of the materials adequate for eachpassivation function to optimize the light extraction efficiency.

FIG. 7 is a sectional view of a light emitting device 103 according to athird embodiment.

A third embodiment may adopt the technical features of the firstembodiment.

The third embodiment may include a light emitting structure 210 havingan inclined side surface to expand a range of an escape cone, therebyimproving light extraction efficiency.

The inclined side surface of the light emitting structure 210 may beformed by performing an etching process in consideration of a propercrystal orientation of a material of the light emitting structure 210.

In the third embodiment, a second passivation layer 132 may have athickness of (λ/4n)×(2m+1) (where, λ is a wavelength of light emittedfrom an active layer, n is a refractive index of the light emittingstructure, and m is zero or a positive integer).

According to the third embodiment, in a case where a chip has an mesaangle θ in shape, a thickness t2 of the second passivation layer 132 maybe increased to (λ/4n)×(2m+1)/cos(x) (where, m is zero or a positiveinteger, x is an angle between zero and θ, and θ is an inclined angle ofthe side surface of the light emitting structure).

A second electrode layer 220 may be disposed under the light emittingstructure 210.

FIG. 8 is a sectional view of a light emitting device 104 according to afourth embodiment. A fourth embodiment may adopt the technical featuresof the second embodiment.

The fourth embodiment may include a light emitting structure 210 havingan inclined side surface to expand a range of an escape cone, therebyimproving light extraction efficiency. The inclined side surface of thelight emitting structure 210 may be formed by performing an etchingprocess in consideration of a proper crystal orientation of a materialof the light emitting structure 210. A second electrode layer 220 may bedisposed under the light emitting structure 210.

According to the fourth embodiment, in a case where a chip has an mesaangle θ in shape, a thickness t2 of the second passivation layer 132 maybe increased to (λ/4n)×(2m+1)/cos(x) (where, m is zero or a positiveinteger, x is an angle between zero and θ, and θ is an inclined angle ofthe side surface of the light emitting structure).

FIG. 9 is a sectional view of a light emitting device 105 according to afifth embodiment.

A fifth embodiment may adopt the technical features of the fourthembodiment.

The light emitting device 105 according to the fifth embodiment mayinclude a light emitting structure 110 including a first conductive typesemiconductor layer 112, an active layer 114, and a second conductivetype semiconductor layer 116 and a pad electrode 160 on a portion of atop surface of the light emitting structure 110.

According to the fifth embodiment, in a multi-passivation layer 130, afirst passivation layer 131 contacting a light extraction structure Pdisposed on a top surface of the light emitting device chip may bedisposed, and then, a second passivation layer 132 contacting a sidesurface of the light extraction structure P may be disposed.

The current embodiment may include a first electrode 140 on the lightemitting structure 110. The pad electrode 160 may be electricallyconnected to the first electrode 140.

The light extraction structure P may be disposed on the top surface ofthe light emitting structure 110 to improve light extraction efficiency.

A second electrode layer 120 may be disposed under the light emittingstructure 110. The second electrode layer 120 may include an ohmic layer122, a reflective layer 124, a coupling layer 125, and a supportsubstrate 126.

A protection member 190 may be disposed outside a lower side of thelight emitting structure 110. A current blocking layer may be disposedbetween the light emitting structure 110 and the ohmic layer 122.

The protection member 190 may be disposed in a circumference regionbetween the light emitting structure 110 and the coupling layer 125.Thus, the protection member 190 has a ring shape, a loop shape, or asquare frame shape. A portion of the protection member 190 mayvertically overlap the light emitting structure 110.

The protection member 190 may increase a distance between side surfacesof the coupling layer 125 and the active layer 114 to prevent thecoupling layer 125 and the active layer 114 from being electricallyshort-circuited to each other.

Also, the protection member 190 may prevent electrical short-circuitfrom occurring in a chip separation process.

The protection member 190 may be formed of an insulative material, amaterial having conductivity less than that of the reflective layer 124or the coupling layer 125, or a material, which forms schottky contactwith the second conductive type semiconductor layer 116. For example,the protection member 190 may be formed of at least one of ITO, IZO,IZTO, IAZO, IGZO, IGTO, AZO, ATO, ZnO, SiO2, SiO_(x), SiO_(x)N_(y),Si₃N₄, Al₂O₃, TiO_(x), TiO₂, Ti, Al, and Cr.

FIG. 10 is a sectional view of a light emitting device package includingthe light emitting device according to the embodiments.

Referring to FIG. 10, a light emitting device package according to theembodiments includes a package body 205, a third electrode layer 213 anda fourth electrode layer 214 disposed on the package body 205, a lightemitting device 100 disposed on the package body 205 and electricallyconnected to the third electrode layer 213 and the fourth electrodelayer 214, and a molding member 240 surrounding the light emittingdevice 100.

The package body 205 may be formed of a silicon material, a syntheticresin material, or a metal material. An inclined surface may be disposedaround the light emitting device 100.

The third electrode layer 213 and the fourth electrode layer 214 areelectrically separated from each other and supply a power to the lightemitting device 100. Also, the third electrode layer 213 and the fourthelectrode layer 214 may reflect light generated in the light emittingdevice 100 to improve light efficiency, and may release heat generatedin the light emitting device 100 to the outside.

The light emitting device 100 may be applicable to a vertical type lightemitting device of FIG. 1, 6, 7, or 8, but is not limited thereto.

The light emitting device 100 may be disposed on the package body 205 oron the third electrode layer 213 or the fourth electrode layer 214.

The light emitting device 100 may be electrically connected to the thirdelectrode layer 213 or/and the fourth electrode layer 214 using one of awire-bonding method, a flip-chip method, and a die bonding method. Inthe current embodiment, the light emitting device 100 may beelectrically connected to the third electrode layer 213 through a wire.Also, the light emitting device 100 may be directly contact the fourthelectrode layer 214 and thus electrically connected to the fourthelectrode layer 214.

The molding member 240 may surround the light emitting device 100 toprotect the light emitting device 100. Also, the molding member 240 mayinclude a phosphor to vary a wavelength of light emitted from the lightemitting device 100.

A plurality of light emitting device packages according to theembodiments may be arrayed on a board. Also, optical members such as alight guide plate, a prism sheet, a diffusion sheet, and a fluorescencesheet may be disposed on a path of light emitted from the light emittingdevice packages. The light emitting device package, the board and theoptical members may function as a backlight unit or lighting unit. Forexample, the lighting system may include a backlight unit, a lightingunit, an indicator unit, a lamp, a streetlamp, etc.

FIG. 11 is a perspective view of a lighting unit 1100 according to anembodiment. The lighting unit 1110 shown in FIG. 11 is an example of thelighting system, but is not limited thereto.

Referring to FIG. 11, the lighting unit 1100 may include a case body1110, a light emitting module 1130 disposed in the case body 1110, and aconnection terminal 1120 disposed in the case body 1110 to receive apower from an external power source.

The case body 1110 may be formed of a material having an improved heatdissipation characteristic. For example, the case body 1110 may beformed of a metal material or resin material.

The light emitting module 1130 may include a board 1132 and at least onelight emitting device package 200 mounted on the board 1132.

A circuit pattern may be printed on an insulator to form the board 1132.For example, the board 1132 may include a printed circuit board (PCB), ametal core PCB, a flexible PCB, or a ceramic PCB.

Also, the substrate 1132 may be formed of a material that caneffectively reflect light. A surface of the substrate 1132 may be coatedwith a colored material, e.g., a white or silver-colored material bywhich light is effectively reflected.

The light emitting device package 200 may be mounted on the board 1132.The light emitting device package 200 may include at least one lightemitting diode (LED) 100. The light emitting diode 100 may include acolored light emitting diode that emits red, green, blue, or whitelight, and an UV light emitting diode that emits ultraviolet (UV) light.

The light emitting module 1130 may include a plurality of light emittingdevice packages 200 to obtain various colors and brightness. Forexample, a white light emitting device, a red light emitting device, anda green light emitting device may be disposed in combination with eachother to secure a high color rendering index (CRI).

The connection terminal 1120 may be electrically connected to the lightemitting module 1130 to supply a power. As shown in FIG. 11, althoughthe connection terminal 1120 is screw-inserted into an external powersource in a socket manner, the present disclosure is not limitedthereto. For example, the connection terminal 1120 may have a pin shape.Thus, the connection terminal 1120 may be inserted into the externalpower source or connected to the external power source using aninterconnection.

FIG. 12 is an exploded perspective view of a backlight unit 1200according to an embodiment. The backlight unit 1200 shown in FIG. 12 isan example of the lighting system, but is not limited thereto.

A backlight unit 1200 according to an embodiment may include a lightguide plate 1210, a light emitting module 1240, a reflective member1220, and a bottom cover 1230, but is not limited thereto. The lightemitting module 1240 may provide light to the light guide plate 1210.The reflective member 1220 may be disposed below the light guide plate1210. The bottom cover 1230 may receive the light guide plate 1210, thelight emitting module 1240, and the reflective member 1220.

The light guide plate 1210 diffuses light to produce planar light. Thelight guide plate 1210 may be formed of a transparent material. Forexample, the light guide plate 1210 may be formed of one of an acrylicresin-based material such as polymethylmethacrylate (PMMA), apolyethylene terephthalate (PET) resin, a poly carbonate (PC) resin, acyclic olefin copolymer (COC) resin, and a polyethylene naphthalate(PEN) resin.

The light emitting module 1240 provides light to at least one surface ofthe light guide plate 1210. Thus, the light emitting module 1240 may beused as a light source of a display device including the backlight unit.

The light emitting module 1240 may contact the light guide plate 1210,but is not limited thereto. In particular, the light emitting module1240 may include a substrate 1242 and a plurality of LIGHT EMITTINGDEVICE packages 200 mounted on the substrate 1242. The substrate 1242may contact the light guide plate 1210, but is not limited thereto.

The substrate 1242 may be a PCB including a circuit pattern (not shown).However, the substrate 1242 may include a metal core PCB or a flexiblePCB as well as the PCB, but is not limited thereto.

The light emitting device packages 200 may have light emitting surfacesthat emit light on the substrate 1242 and are spaced a predetermineddistance from the light guide plate 1210.

The reflective member 1220 may be disposed below the light guide plate1210. The reflective member 1220 reflects light incident onto a bottomsurface of the light guide plate 1210 to proceed in an upward direction,thereby improving brightness of the backlight unit. For example, thereflective member may be formed of one of PET, PC, and PVC, but is notlimited thereto.

The bottom cover 1230 may receive the light guide plate 1210, the lightemitting module 1240, and the reflective member 1220. For this, thebottom cover 1230 may have a box shape with an open upper side, but isnot limited thereto.

The bottom cover 1230 may be formed of a metal material or a resinmaterial. Also, the bottom cover 1230 may be manufactured using a pressforming process or an extrusion molding process.

In the light emitting device, the light emitting device package, and thelighting system according to the embodiments, the multi-passivationlayer having the refractive indexes different from each other may bedisposed on the side surface and the top surface of the light emittingstructure may be provided to obtain the optimized light amount.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A light emitting device comprising: a lightemitting structure comprising a first conductive type semiconductorlayer, a second conductive type semiconductor layer, and an active layerbetween the first conductive type semiconductor layer and the secondconductive type semiconductor layer; and, a passivation layer on thelight emitting structure, wherein the passivation layer comprises: afirst passivation layer on a top surface of the light emittingstructure; and a second passivation layer having a refractive indexdifferent from that of the first passivation layer, the secondpassivation layer being disposed on a side surface of the light emittingstructure.
 2. The light emitting device of claim 1, wherein the secondpassivation layer has a refractive index greater than that of the firstpassivation layer.
 3. The light emitting device of claim 1, wherein thesecond passivation layer is formed also on the first passivation layerdisposed on the top surface of the light emitting structure.
 4. Thelight emitting device of claim 1, wherein the first passivation layerhas a refractive index less than that of the light emitting structure.5. The light emitting device of claim 1, wherein the second passivationlayer has a thickness of (λ/4n)×(2m+1) (where, λ is a wavelength oflight emitted from the active layer, n is a refractive index of thelight emitting structure, and m is zero or a positive integer).
 6. Thelight emitting device of claim 1, further comprising a light extractionstructure on the light emitting structure.
 7. The light emitting deviceof claim 6, wherein at least one layer of the first passivation layerand the second passivation layer comprises the light extractionstructure on a surface thereof.
 8. The light emitting device of claim 1,wherein at least one layer of the first passivation layer and the secondpassivation layer comprises the light extraction structure on a surfacethereof, and the light extraction structure on the surface of the atleast one layer of the first passivation layer and the secondpassivation layer is disposed along with a shape of the light extractionstructure on the light emitting structure.
 9. The light emitting deviceof claim 1, wherein the light emitting structure comprises an inclinedside surface.
 10. The light emitting device of claim 1, wherein thesecond passivation layer has a thickness of (λ/4n)×(2m+1)/cos(x) (where,m is zero or a positive integer, x is an angle between zero and θ, and θis an inclined angle of the side surface of the light emittingstructure).
 11. The light emitting device of claim 1, wherein the secondpassivation layer includes an anti-reflection coating condition.
 12. Thelight emitting device of claim 1, further comprising a second electrodelayer under the light emitting structure.
 13. The light emitting deviceof claim 12, wherein the second electrode layer comprises at least oneof an ohmic layer, a reflective layer, a coupling layer, and a supportsubstrate.
 14. The light emitting device of claim 13, further comprisinga protection member outside a lower side of the light emittingstructure, wherein the protection member is disposed in a circumferenceregion between the light emitting structure and the coupling layer. 15.The light emitting device of claim 14, wherein the protection membercomprises a ring shape, a loop shape, or a square frame shape.
 16. Thelight emitting device of claim 14, wherein a portion of the protectionmember is vertically overlap the light emitting structure.
 17. The lightemitting device of claim 12, further comprising a current blocking layerbetween the light emitting structure and the second electrode layer.